The goal of this project is to identify, isolate and characterize islet cell surface molecules using techniques recently developed by Milstein and coworkers. These techniques are based on the production of anti-cell surface monoclonal antibodies by hybrid cell lines. I have previously used these methods to define nervous system cell surface differentiation antigens. With these techniques one can derive monoclonal antibodies to cell surface antigens without prior purification of the antigens of interest. Milligram quantities of monoclonal antibodies can be produced which allow subsequent isolation of the antigen recognized by the antibody as well as exploration of an antigen's physiologic function. Basic to this project is the availability of islet cells to be used both as immunogens and as targets to assay for the production of anti-cell surface antibodies. I have available a rat transplantable insulinoma, a transplantable hamster insulinoma, access to members of my division with expertise in isolating islet cells from a number of animals, and a human islet cell culture which I have recently derived from a malignant insulinoma. The monoclonal antibody techniques depend on rapid and sensitive screening methods to identify anti-cell surface antibodies. I have adapted and developed semi-automated assays (I125-Protein A radioassay and Cr51 cytotoxicity) to measure anti-cell surface antibodies which are performed in 96 well microtiter plates. Finally, I propose to apply cell surface antibody assays in combination with monoclonal anti-islet cell antibodies to study the anti-islet cell antibodies of normals, diabetics and a group of polyglandular failure patients.